1. Field of the Invention
The field of the invention is data processing, or, more specifically, methods, apparatus, and products for clock signal synchronization among computers in a network.
2. Description of Related Art
The development of the EDVAC computer system of 1948 is often cited as the beginning of the computer era. Since that time, computer systems have evolved into extremely complicated devices. Today's computers are much more sophisticated than early systems such as the EDVAC. Computer systems typically include a combination of hardware and software components, application programs, operating systems, processors, buses, memory, input/output devices, and so on. As advances in semiconductor processing and computer architecture push the performance of the computer higher and higher, more sophisticated systems have evolved to take advantage of the higher performance of the hardware, resulting in computer systems today that are much more powerful than just a few years ago.
One of the areas in which considerable progress has been made is in scalable, synchronous operations among multiple computers. A ‘switched fabric,’ such as Fibre Channel or InfiniBand™, for example, can connect many devices through high-speed interconnections, so that the separate computers can in effect operate synchronously almost as a single machine. Switched fabric networks support redundant paths between multiple devices, forming a mesh network with devices being on the ‘edges’ of the mesh. One of the advantages of this topology is failover, meaning that in case one link breaks or a switch is out of order, communications among machines in the network can traverse alternate paths. Another advantage of such a topology is scalability, that more connections can be added as the number of endpoints increases so the route length (and thus, latency and throughput) can remain constant for point-to-point communications among the individual machines connected to the network. Scalable computing relies on building blocks that can operate independently. When operating in a multi-node, scaled environment, the difference in clock frequency among the various building block nodes impose additional latency to compensate for the varying offset frequency when communicating among the nodes and retiming the data for the local clock domain. While elastic buffers and asynchronous operation support this multi-frequency node communication, such operations require cumbersome additional logic and latency-management operations to provide adequate buffering and retiming of high speed signals among computers in such networks.